The present invention relates to a power supply for electronic equipment and more particularly to a proportional pulse current feedback power supply.
In the prior aft power supplies,upon application of prime power,high voltage is developed after sufficient filament warm up time across a plurality of capacitors. Feedback from the most negative one of the voltages maintains these voltages, establishing a regulated power supply. When a power supply is employed in conjunction with a traveling wave tube, and radio frequency (RF) transmission is not required, the traveling wave tube draws no current from the power supply. However, when RF transmission is required, the traveling wave tube demands full load from the power supply. This is a no-load to full-load step-load on the power supply. Its response to this is dependent upon a number of factors.
The traveling wave tube requirement for a step load is that the droop or pulse regulation of the helix and first and second collectors be held within a few percent (typically less than 5%) of the nominal voltage.
A number of approaches to meet this requirement have been tried in the past, in many cases with partial success. A brief review follows.
(A) The droop or pulse regulation can be minimized by increasing the total capacitance of the capacitors providing the voltage sufficient to hold the charge until the regulator response is stabilized.
(B) An alternate method would be to increase the bandwidth and slew rate to maintain the regulation.
(C) An additional scheme is to provide an anticipation signal into the feedback circuit that commands increased output power before a substantial droop results. This approach is called "feed forward" in the art.
Although combinations of the above approaches have been used, the results are not always satisfactory. With approach (A) the resultant size of the capacitors makes the power supply prohibitively large especially for airborne applications. With approach (B) the bandwidth cannot be achieved due to the component limitations to meet the pulse regulation, since the inherent switching noise interferes with performance. Approach (C) has been successfully used, but for limited conditions; It will frequently result in considerable overshoot and ringing.